Evaporative heat exchanger



J. ENGALITCHEFF, JR, ET AL 3,385,352

EVAPORATIVE HEAT EXCHANGER 4 Sheets-Sheet 1 May 28, 1968 Filed Sept. 7, 1966 mm an M ECU m .wQr a IE- m 5 Wm M H Hrw y 1968 J. ENGALITCHEFF. JR., ET AL 3,385,352

EVAPORATIVE HEAT EXCHANGER Filed Sept. 7, 1966 4 Sheets-Sheet 2 All? Fig. 3

REE

MAKE-UP WATER 40 //2 INVENTORS JOHN ENGAL/TGHEFF, JR,

THOMAS E FAG/US, WILSON E. BRADLEY ORNEYS y 1968 J. ENGALITCHEFF, JR, ET AL 3,385,352

EVAPORATIVE HEAT EXCHANGER Sheets-Sheet 5 Filed Sept.

INVENTORS JOHN ENGAL/TGHEFF, JR,

THO/W5 E FAG/US, WILSON E. BRADLEY M M ATTORNEYS y 1968 J. ENGALITCHEFF, JR, ET AL 3,385,352

EVAPORATIVE HEAT EXCHANGER Filed Sept. 7, 1966 Fig. 5

4 Sheets-Sheet RE F.

FLU/D OUT MAKE-UP WA TEE 27m, 190% wfiw ORNEYS United States Patent 3,385,352 EVAPORATIVE HEAT EXCHANGER .Iohn Engalitchelf, Jr., Gibson Island, Thomas F. Facius, Baltimore, and Wilson E. Bradley, Ellicott City, Md., assignors to Baltimore Aircoil Company, Inc., Baltimore, Md., a corporation of Maryland Filed Sept. 7, 1966, Ser. No. 577,742 1 Claim. (Cl. 16560) ABSTRACT OF THE DISCLOSURE An evaporative heat exchanger of the draw through (induced draft) type having an inner casing and an outer casing with a coil between these casings containing fluid to be cooled. A motor turns a central shaft which powers both a propeller type fan for air circulation and a centrifugal pump for water circulation. Air enters through the outer casing, moves downwardly between the casings, over the coil, upwardly and out through the fan. Water is pumped from a sump region upwardly through a plurality of tubes which rotate with the central shaft to a trough and flows from it through a plurality of pipes to a pan above the coil. The water then moves downwardly over the coil along with the circulating air.

The present invention relates to evaporative heat exchangers, and more particularly to evaporative condensers having improved water distribution systems.

In an evaporative condenser, a refrigerant or other fluid to be cooled and/ or condensed is circulated through a coil or tube bank which is disposed in a chamber having a sump at its bottom. The outside of the coil is kept wet and air flows over the wet surfaces causing evaporation, the heat for which is extracted from the fluid within the coil. The portion of the water which flows over the coils and which does not evaporate is collected in a sump and is recycled.

Australian Patent No. 114,639 describes an evaporative condenser of the subject type in which a common shaft actuates a cooling air fan and a slinger for spraying water outwardly over the coil in the form of an annular spray. This spray pattern is undesirable where the coil is not of annular configuration, and the airflow through the condenser may impede proper distribution of the spray over the entire coil. Furthermore, embodiments described in said patent wherein the water is sprayed along the pump axis through a plurality of apertures in an inverted truncated cone cause difficulties in balancing the internal pressures within the unit to achieve proper fluid distribution. Such orifices may require recalibration after 21 period of use. Such structures have the disadvantage that the amount of water contacting a given tube of the coil is dependent upon the position of the tube since the lower tubes are contacted directly by part of the spray as well as by water draining off of the upper tubes.

It is a primary object of the present invention to provide an evaporative heat exchanger of the above described type which is not subject to the above described prior art problems.

Another object of the present invention is to provide an evaporative heat exchanger which has an improved water distribution system.

The above and other objects and advantages of this invention will become more apparent upon consideration of the following detailed description taken in conjunction with the drawings wherein:

FIG. 1 is an elevational view of an evaporative heat exchanger in accordance with the present invention;

FIG. 2 is a partial plan view of the heat exchanger shown in FIG. 1;

FIG. 3 is a vertical sectional view through the heat exchanger with some parts rotated from their actual position for the sake of clarity;

FIG. 4 is a horizontal cross-sectional view taken on the line 44 of FIG. 3;

FIG. 5 is a horizontal cross-sectional view taken on the line 5-5 of FIG. 3;

FIG. 6 is a partial vertical cross-sectional view showing details of the drip pan and of a cooling water purge system; and

FIG. 7 is a partial vertical cross-sectional view of the lower end of the pump assembly.

The following brief description of the invention will faciltiate understanding of the subsequent detailed description of the invention. In one of its broader aspects, the present invention relates to an improved cooling water distribution system including a centrifugal pump which has its lower end disposed in the sump. Water is dis charged from the upper end of the pump into a trough. Conduit means convey the water from the trough to a pan which is positioned above the coil and is provided with means for distributing the water onto the coil. A blower is provided for causing air to flow over the coil, and preferably the blower and centrifugal pump are mounted upon a common shaft. This arrangement eliminates the necessity of separate motors, starters, etc. for the blower and pump.

In a presently preferred embodiment, air is drawn into the heat exchanger through an annular air inlet disposed below the water distribution pan. The air and water thus flow concurrently downward over the coil. Means are provided to change the direction of airflow through 180 in a region just above the bottom of the coil and the water level in the sump. The water being heavier is separated from the air due to the change in direction of flow and falls into the sump so that the water is efliciently separated from the air without the necessity of providing mist eliminators, which are costly and diflicult to fabricate.

Referring now to the drawings, and more particularly to FIG. 3, reference numeral 10 designates a coil for containing refrigerant or other fluid. The coil is positioned between an inner casing 12 and an outer casing 14 with the individual tubes of the coil supported by four spaced support grids constituted by a plurality of intersecting vertical rods 16 and horizontal rods 18 'and which are supported on flanges 20. The refrigerant enters the coil via an inlet line 22 and an inlet header 24. After being condensed, the fluid is collected in header 26 and is passed to the refrigeration system or other point of use through line 2-8. If the unit is used for cooling without condensing the flow of liquid is reversed with the liquid to be cooled entering through conduit 28 and leaving through conduit 22.

Air is drawn into the heat exchanger through an air inlet constituted by a pair of arcuate screens 30 which are detachably secured to a frame member 32 by clamps 34 as shown in FIG. 1. The entering air flows downwardly over the coils concurrently with water droplets from a drip pan 36 which has a plurality of regularly spaced apertures 38 in its bottom. Heat is extracted from the fluid in the coil 10 by the combined action of the air and water, with the principal portion of the heat being extracted by vaporization of a portion of the water flowing over the coil. The air and water leaving the coil are directed downwardly towards a sump 40. The air is turned upwardly through as shown by the arrows in FIG. 3, into an air exit conduit formed by the inner surface of the casing 12 and the outer surface of a smaller additional casing 42. The water being heavier, is separated from the air due to the change of direction and falls into the sump 40. The water level in the sump is constantly regulated by a valve 44 and a float 46 to compensate for the small portion of the water that is evaporated and otherwise lost from the unit.

The deflected air is drawn upwardly between casings 12 and 42 by a blower 45 and is vented to the atmosphere through a screened outlet 47. The blower is mounted upon a shaft 48 which is driven by a motor 50 via pulleys 52, 54 and an endless belt 56. The motor 50 is partially covered by a housing 58 having an internal screen 60 which is between the top of the motor and the bottom of the pulley 52. The shaft 48 is supported in a pair of spaced bearings 62, 64 which are mounted on the ends of T-shaped supporting frames 66, 68.

Water from the sump 40 is taken up by a centrifugal pump generally designated by reference numeral 70. The centrifugal pump of the illustrated embodiment comprises four open-ended conduits 72 which are disposed about the shaft 48 and are secured thereto by means of three spaced assemblies each consisting of a collar 74 and an apertured collar plate 76.

As illustrated in FIG. 7, the lower ends 78 of the pump conduits 72 slant downwardly and inwardly and constitute inlets to the centrifugal pump. The lower portions of conduits 72 are imbedded in a base 80 which is made of a suitable synthetic plastic, such as a polyester. The base is in the form of an inverted truncated cone terminating with upper vertical sides. The diameter and taper of the cone are functions of the water flow requirements. This design of the base results in a smooth operation with a minimum of water turbulence from the rotating structure with a resulting decrease in drag and an increase in efficiency.

During operation, water is, in effect, sucked into the inlets to the conduits 72. Centrifugal force, which is a function of both the rotational speed and the amount of taper of the ends 78 of the conduits in a radial direction (as shown by the distance A in FIG. 7), causes the water to flow up conduits 72 and to spill out the upper ends of the conduits into an annular trough formed by an annular L-shaped member 82 and the inner surface of casing 42. A cover 83 seals the top of the annular trough to prevent loss of water into the air stream.

The bottom edge of casing 42 terminates slightly above the normal water level in sump 40 when the pump is not in operation, for example, about one half inch above the water level. This spacing, as compared to having the casing project into the water in the sump, is particularly advantageous at start-up and reduces the power requirements. When the pump is started, the forces imparted to the water by the rotation of base result in an upward surging of the water in an annular region in the vicinity of the bottom edge of the casing 42 so that the water tends to seal the bottom edge of the casing.

Referring now to FIG. 4, a plurality of radial conduits 84 convey the water outwardly to the annular drip pan 36. The conduits have mitered inlet openings 86 for receiving the water which has a swirling motion in the annular trough as shown by the arrows in FIG. 4. Conduits 84 may be secured within apertures in the casings 12 and 42 by a suitable means such as rubber grommets 88.

The drip pan 36 has a pair of removable covers 90, 92 each having handles 96. The covers 90, 92 are positioned so that a workman may have ready access to the drip pan 36 for cleaning while the unit remains in operation. Similarly, for maintenance purposes, the outer casing 14 has a removable access plate 98 which has a handle 100 and which is secured to the casing by any suitable means such as by bolts provided with wing nuts 102.

It is well known that in units of this nature scale and other contaminants accumulate in the cooling water. Although such contaminants can be tolerated reasonably well in the present unit, a blow down line 104 which is best illustrated in FIG. 6 is provided to continually remove a small portion of the water flowing in one of the radial conduits 84. The blow down line 104 extends through a suitable grommet 106 in an opening in the wall of the conduit 84 and has a small opening 108 in one side through which the water is blown down. The upper end of line 104 extends above the normal water level in the conduit 84, and has a small air vent hole 109. The lower end of line 104 is received within a pipe 110 which is threadably connected to a drain pipe 112 as shown in FIG. 3. A rod 114 is welded or otherwise suitably secured to the pipe 110 and functions as a lever so that the pipe 110 may be detached from the drain pipe 112 when desired.

While the present invention has been described in terms of a presently preferred embodiment, it is apparent that many changes and modifications may be made without departing from the spirit of the invention. For example, the pump conduits 72 might be spaced a greater distance outwardly from the shaft 48 with a corresponding increase in the length of the inclined conduit ends 78. Such an arrangement increases the effective radial distance A of FIG. 7 thereby increasing the centrifugal force available to elevate the water out of the sump. Since there are economic limitations upon the speed at which the blower may rotate, it is preferable to increase the centrifugal force, when necessary, by increasing the effective radial distance A. In such an arrangement, the shaft 48 could be extended and provided with a suitable support bearing positioned within the sump. It is intended to encompass all such changes and modifications that come within the scope of the appended claim.

What is claimed is:

1. Apparatus for extracting heat from fluids comprising an outer casing, means defining a sump within said outer casing, an inner casing having lower edge portions thereof disposed above the normal water level in said sump, a coil positioned between said inner and said outer casings and adapted to contain the fluid from which heat is to be extracted, an air inlet provided in said outer casing, an additional casing disposed within said inner casing and cooperating with said inner casing to form an upward air flow passage, a blower to cause air to flow from said air inlet downwardly over said coil and subsequently upwardly between said inner casing and said additional casing, drive means for rotating said blower including a driven shaft positioned essentially centrally within said additional casing, and distribution means for distributing cooling water downwardly over said coil and into said sump, said distribution means including a centrifugal pump actuated by said shaft and extending into said sump, said pump including at least one open-ended vertical conduit connected to said shaft and rotated therewith, wall portions disposed within said additional casing and together with the inner surface of said additional casing forming a substantially annular trough for receiving water from said pump, and a plurality of radially disposed conduits extending from said trough to said pan, a blow down line extending into one of said conduits intermediate the ends thereof, said line being provided with an opening adapted to receive water to be blown down, said line having an upper end above the normal water level in said conduit, and said upper end having a vent hole therein, an annular pan positioned above said coil and having means for distributing water onto said coil.

References Cited UNITED STATES PATENTS 5/1950 Bockmeyer 62310 6/1959 Stutz 62310 

